Sources: U.S. Food and Drug Administration (FDA) Compounding and the FDA (503A & 503B guidance) FDA warning letters on unapproved peptide products National Institutes of Health (NIH) PubMed Best BPC 157 Oral Supplements: ProHealth's Triple Tested Formula Examined as Peptide Quality Verification Becomes Consumer Priority Heading Into 2026 The FDA has issued warning letters to multiple companies marketing compounded Retatrutide, an investigational drug from Eli Lilly still in Phase II trials. While early studies have shown promising weight loss results, Retatrutide FDA moves toward easing restrictions on certain peptides BioPharma Dive FDA May Reverse Ban on 14 PeptidesWhat It Means for Your Beauty Routine Allure